U.S. patent number 4,771,767 [Application Number 06/825,251] was granted by the patent office on 1988-09-20 for apparatus and method for maintaining vertebrae in a desired relationship.
This patent grant is currently assigned to AcroMed Corporation. Invention is credited to Arthur D. Steffee.
United States Patent |
4,771,767 |
Steffee |
September 20, 1988 |
Apparatus and method for maintaining vertebrae in a desired
relationship
Abstract
An apparatus and method for moving a vertebra to a desired
relationship with other vertebrae and for maintaining the desired
relationship. Mounting blocks are attached to the vertebrae. Pivot
members are threaded onto a rod. The pivot members are received in
the mounting blocks with the rod extending between two mounting
blocks. The rod is rotated to move a vertebra relative to the other
vertebrae. The mounting blocks are then tightened around the pivot
members to maintain the vertebrae in the desired relationship.
Inventors: |
Steffee; Arthur D. (Moreland
Hills, OH) |
Assignee: |
AcroMed Corporation (Cleveland,
OH)
|
Family
ID: |
25243515 |
Appl.
No.: |
06/825,251 |
Filed: |
February 3, 1986 |
Current U.S.
Class: |
606/256; 606/258;
606/279 |
Current CPC
Class: |
A61B
17/7002 (20130101); A61B 17/7044 (20130101); A61B
17/704 (20130101); A61B 17/7041 (20130101) |
Current International
Class: |
A61B
17/70 (20060101); A61F 005/04 () |
Field of
Search: |
;128/92YM,92ZW,69,92YF
;623/17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2821678 |
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Nov 1979 |
|
DE |
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3132520 |
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Jun 1982 |
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DE |
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839515 |
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Jun 1981 |
|
SU |
|
Primary Examiner: Crowder; Clifford D.
Attorney, Agent or Firm: Tarolli, Sundheim & Covell
Claims
Having described my invention, I claim:
1. A method for moving a first vertebra to a desired relationship
with a second vertebra and for maintaining the first and second
vertebrae in a desired relationship, said method comprising:
forming an opening in a first vertebra;
forming an opening in a second vertebra;
threading fasteners into the openings in the first and second
vertebrae;
providing mounting blocks for attachment with the first and second
vertebrae, each of the mounting blocks having first and second
halves which cooperate to form a chamber for receiving a pivot
member;
placing a first half of one mounting block onto the fastener in the
first vertebra and a first half of another mounting block onto the
fastener in the second vertebra;
providing a first pivot member having a righthand internally
threaded portion and a second pivot member having a lefthand
internally threaded portion;
providing a rod having a first end portion with a righthand thread
and a second end portion with a lefthand thread;
threading the first pivot member onto the first end portion of the
rod;
threading the second pivot member onto the second end portion of
the rod;
placing the first pivot member into the portion of the chamber
formed in the first half of the one mounting block on the first
vertebra with the rod extending from the one mounting block towards
the second vertebra;
placing the second pivot member into the chamber in the other
mounting block on the second vertebra;
placing a second half of the one mounting block onto the fastener
in the first vertebra;
placing a second half of the other mounting block onto the fastener
in the second vertebra;
tightening nuts on respective fasteners with sufficient force to
clamp the mounting blocks around the respective pivot members
allowing pivotal movement of the pivot members relative to the
mounting blocks and preventing rotational movement of the pivot
members about the longitudinal central axis of the rod;
rotating the rod relative to the first and second pivot members to
move the first vertebra relative to the second vertebra to a
desired relationship; and
thereafter, tightening the nuts against the mounting blocks
preventing pivotal and rotational movement of the pivot members
relative to the mounting blocks thereby maintaining the desired
relationship.
2. An apparatus comprising:
a first mounting block connectible with a first vertebra;
a second mounting block connectible with a second vertebra;
first fastening means for extending through an opening in said
first mounting block to connect said first mounting block with a
first vertebra;
second fastening means for extending through an opening in said
second mounting block to connect said second mounting block with
the second vertebra;
rod means rotatable about its longitudinal central axis extending
between said first and second mounting blocks; and
means for pivotally connecting a first end portion of said rod
means with said first mounting block and a second end portion of
said rod means with said second mounting block and for supporting
said rod means for rotation relative to said first and second
mounting blocks, said means for pivotally connecting having a
threaded portion cooperating with a threaded end portion of said
rod means to effect relative movement of the first and second
vertebrae upon rotation of said rod means;
each of said first and second mounting blocks including a pair of
halves, each of said pair of halves having a surface defining a
portion of a chamber for receiving said means for pivotally
connected when said halves are pressed together by tightening said
respective fastening means against said mounting block, said
mounting block also having a surface defining another opening for
receiving said rod means therein and extending through said
mounting block to said chamber in a direction transversely to said
opening for said fastening means.
3. An apparatus as set forth in claim 2 wherein said means for
pivotally connecting includes pivot members of a generally
spherical configuration, each of said pivot members having an
internally threaded portion passing approximately through the
center of said pivot member for receiving said externally threaded
end portion of said rod means, said chamber in each of said first
and second mounting blocks being of a generally spherical
configuration for receiving a respective one of said pivot
members.
4. An apparatus as set forth in claim 2 wherein said means for
pivotally connecting includes pivot members of a generally
cylindrical configuration, each of said pivot members having an
internally threaded portion transversely intersecting the
longitudinal axis of said pivot member for receiving said
externally threaded end portion of said rod means, said chamber in
each of said first and second mounting blocks being of a generally
cylindrical configuration for receiving a respective one of said
pivot members.
5. An apparatus comprising:
a first mounting block connectible with a first vertebra;
a second mounting block connectible with a second vertebra;
first fastening means for connecting said first mounting block with
the first vertebra;
second fastening means for connecting said second mounting block
with the second vertebra;
rod means rotatable about its longitudinal central axis extending
between said first and second mounting blocks; and
means for pivotally connecting a first end portion of said rod
means with said first mounting block and for pivotally connecting a
second end portion of said rod means with said second mounting
block and for supporting said rod means for rotation relative to
said first and second mounting blocks, said means for pivotally
connecting having a threaded portion cooperating with a threaded
end portion of said rod means to effect relative movement of the
first and second vertebrae upon rotation of said rod means;
each of said first and second mounting blocks including a pair of
halves, each of said pair of halves having a surface defining a
portion of a chamber for receiving said means for pivotally
connecting when said halves are pressed together, each of said pair
of halves also having a surface defining a first opening in each of
said first and second mounting blocks and which first opening
extends through said mounting block to said chamber for receiving
said rod means, each of said first and second mounting blocks
including a surface defining a second opening therethrough and
extending in a direction transverse to said first opening, said
first and second fastening means extending through the respective
second opening in each respective mounting block to press said
halves of said mounting blocks together.
Description
BACKGROUND OF THE INVENTION
The present invention relates to the correction of spinal
deformities. Specifically, it relates to moving a vertebra to a
desired relationship with other vertebrae and maintaining the
desired relationship.
Devices for correcting spinal column deformities are known. U.S.
Pat. No. 3,997,138 discloses a device which has a pair of flexible
rods or cables to maintain adjacent vertebrae in a desired
relationship. The rods or cables are secured to fasteners connected
with the vertebrae.
Devices which include rigid plates are also known for securing
vertebrae in a desired relationship. The plates are relatively
heavy. Each plate has longitudinal slots formed therein which do
not permit flexibility in locating fasteners laterally in the
vertebrae.
Another known device for correcting spinal deformities is a ratchet
system. The ratchet system includes a rod and ratchet blocks which
engage the rod. The rod spans several vertebrae. The ratchet blocks
have hooks. The hooks grab around pedicles on the vertebrae. The
hooks are then drawn together by the rod to apply a desired
correction to the spinal column. The ratchet system can only
compress the spinal column.
In another device, the corrective forces are applied by two steel
rods which are wired around the spine. The rods are not directly
attached to all the vertebrae that the rods span. Maintaining a
desired spatial relationship among the vertebrae spanned by the
rods is difficult.
Another known spinal corrective device is disclosed in U.S. Pat.
No. 4,041,939. The device includes fasteners which are threaded
into the vertebrae. A cable is threaded through openings in the
head of each fastener. Tension is applied to the cable to move the
vertebrae to a desired relationship. The fasteners are crimped
around the cable to maintain the desired relationship. This device
can only compress the spinal column. Once the cable is crimped into
place, no further adjustment is possible.
SUMMARY OF THE INVENTION
The present invention provides a series of adjustable length links
to move a vertebra to a desired relationship with other vertebrae
and to maintain the vertebrae in the desired relationship. The
links can be subjected to either compressive or tensile forces.
Each link interconnects two adjacent vertebrae. Each link is
adjustable independent of the other links. Thus, the spacing
between a pair of vertebrae can be adjusted while the spacing
between other vertebrae is maintained constant.
Each link includes a rod having pivot members threaded on each end
portion of the rod. The pivot members are connected with adjacent
vertebrae by mounting blocks fastened to individual vertebra. To
vary the spacing between the adjacent vertebrae, the rod is rotated
in order to change the spacing between two pivot members. Thus,
since the pivot members are connected with adjacent vertebrae, the
space between the adjacent vertebrae is also varied.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features of the present invention will become apparent to
those skilled in the art to which the invention relates from a
reading of the following specification made with reference to the
accompanying drawings, in which:
FIG. 1 is a dorsal view of a portion of a spinal column with an
apparatus constructed in accordance with the present invention
installed to maintain a desired relationship of the vertebrae;
FIG. 2 is an enlarged schematic illustration of a spinal column
having a displaced vertebra;
FIG. 3 is an enlarged schematic view, similar to FIG. 2,
illustrating the apparatus installed on a spinal column before
moving the displaced vertebra to a desired relationship;
FIG. 4 is an enlarged schematic view, similar to FIG. 3,
illustrating the present invention installed on a spinal column
after moving the displaced vertebra to the desired
relationship;
FIG. 5 is an enlarged schematic view, similar to FIG. 4,
illustrating another application of the present invention installed
on a spinal column;
FIG. 6 is a perspective view illustrating an adjusting rod;
FIG. 7 is an exploded fragmentary perspective view illustrating
dual spherical pivot members, a mounting block, adjusting rods, and
fastener assembly of the apparatus in FIG. 1;
FIG. 8 is an exploded fragmentary perspective view illustrating a
single spherical pivot member, mounting block, adjusting rod, and
fastener assembly of the apparatus in FIG. 1; and
FIG. 9 is a partially exploded fragmentary perspective view
illustrating a single cylindrical pivot member, adjusting rod, and
fastener assembly.
DESCRIPTION OF SPECIFIC PREFERRED EMBODIMENTS
A pair of assemblies 20 for moving a vertebra 22a to a desired
relationship with other vertebrae 22b, 22c and for maintaining the
desired relationship are illustrated in FIG. 1 connected with a
human spinal column 24. Each of the assemblies 20 includes
adjusting rods 32 connected with mounting blocks 34, 36 which are
attached to individual vertebrae 22 by fastener assemblies 42.
The adjusting rods 32 are connected with the spinal column 24 to
move a vertebra 22a to a desired relationship with other vetebrae
22b, 22c and to maintain the vertebrae 22 in a desired
relationship. In order to maintain vertebra 22a in the desired
relationship, as illustrated in FIG. 1, two adjacent vertebrae 22b,
22c on each side of vertebra 22a have the mounting blocks 34, 36
attached. This serves as an anchor from which to position vertebra
22a relative to. The vertebra 22a is moved relative to vetebrae
22b, 22c by rotating the adjusting rods 32 which interconnect the
vertebra 22a with vertebrae 22b.
Before installing the assemblies 20, a vertebra 22a (FIG. 2) is
displaced relative to adjacent vertebrae 22b, 22c which are in a
desired relationship in the spinal column 24. The vertebra 22a is
illustrated displaced in the dorsal and sagittal directions. It
will be obvious that the vertebra 22a could be displaced in just
the dorsal direction or just the sagital direction.
To install the assemblies 20, the spinous processes 44 (FIG. 2)
must be removed from the vertebrae 22 which will have the
assemblies 20 attached. The spinous processes 44 must be removed so
that they will not interfere with the attachment and adjustment of
the assemblies 20. FIG. 2 illustrates the spinous processes removed
from the vertebrae 22a, 22b, and 22c which will have the assemblies
attached.
Two openings 46 are formed in each of the vertebrae 22a, 22b, 22c
for receiving force transmitting members. The openings are formed
so that they will be in approximate vertical alignment when the
vertebrae 22a, 22b, 22c are in the desired relationship. Force
transmitting members 52 (FIG. 7) are then threaded into the
openings 46 so that part of each force transmitting member extends
from the vertebra 22.
A first half 53a, 53b (FIGS. 7 and 8) of the mounting blocks 34, 36
for connecting pivot members 54 to the vertebrae 22 is received on
the force transmitting member 52 which extends from the vertebra.
Pivot members 54 are threaded onto the end portions of the
adjusting rods 32. Each adjusting rod 32 (FIG. 6) has an end
portion with a righthand thread 55a and an end portion with a
lefthand thread 55b. The pivot members 54 (FIGS. 7 and 8) are
received in chambers 58. A second half 62a, 62b of the mounting
blocks 34, 36 is received on the force transmitting member 52. A
nut 64 is sufficiently tightened onto the force transmitting member
52 to allow pivotal movement of the pivot members 54, but to
restrict their rotational movement, relative the mounting blocks
34, 36. Each adjusting rod 32 is rotated to move the vertebrae 22
to a desired relationship. The direction of rotation of the
adjusting rod 32 depends upon whether the distance between the
pivot members 54 threaded onto the rod is to increase or decrease.
The nut 64 is then further tightened to prevent any pivotal
movement of the pivot joint 54 to maintain the vertebrae 22 in the
desired relationship.
An alternative application of the present invention is illustrated
in FIG. 5. A single assembly 20 is attached to the spinal column 24
to maintain the vertebrae 22 in a desired relationship. The
structure of the single assembly 20 in FIG. 5 is the same as that
for either of the assemblies in FIG. 4.
The fastener assembly 42 (FIG. 4) connects a mounting block 34 or
36 with a vertebra 22 and presses the mounting block against the
pivot members 54 (FIGS. 7 and 8). The fastener assembly 42 includes
a force transmitting member 52 having a first threaded portion 72
and a second threaded portion 74. The first threaded portion 72 has
a relatively large diameter helix for threading into an opening 46
formed in a vertebra 22. The first threaded portion 72 has a
substantially larger crest diameter than the inside diameter of the
opening 46.
As the first threaded portion 72 is threaded into the opening 46,
the helix cuts into the cylindrical side surface of the opening to
firmly attach the force transmitting member 52 to the vertebra 22.
The force transmitting member 52 is threaded into the vertebra 22
by placing a tool (not shown) on the hex head portion 78. The tool
and force transmitting member 52 are then rotated until the desired
depth of engagement with the vertebra 22 is obtained. The force
transmitting member 52 is made from a surgical grade stainless
steel or titanium.
The second threaded portion 74 of the force transmitting member 52
has a standard external screw thread for engaging standard internal
threads of the nut 64. The nut 64 has a standard hexagonal external
configuration for a suitable tool to engage for rotating the nut
relative to the second threaded portion 74. The nut 64 is rotated
until it abuttingly engages a side of the second half 62a, 62b of a
mounting block 34, 36. Initally, the nut 64 is rotated until the
mounting block 34, 36 is pressed against the vertebra 22 with
sufficient force to prevent the pivot member 54 from rotating but
allowing pivotal movement. The adjusting rods 32 are then rotated
about their longitudinal axes to position the vertebrae 22 in a
desired relationship. The nut 64 is then rotated to a final
position where the pivot member 54 is prevented from further
pivotal movement, in order to maintain the vertebrae 22 in the
desired relationship. The threaded portion 74 which extends beyond
the nut 64 is then trimmed off adjacent to the nut. Force
transmitting member 52 has the same general construction disclosed
in U.S. Pat. No. 4,611,581 for "Apparatus for Straightening Spinal
Cclumns", by Arthur D. Steffee.
The adjusting rod 32 (FIGS. 3 and 4) interconnects, varies, and
maintains the position of two vertebrae 22. The adjusting rod 32 is
made from a surgical grade stainless steel or titanium. Before each
adjusting rod 32 (FIG. 6) is installed to connect two vertebrae 22,
it has a pair of pivot members 54 (FIG. 7) threaded onto end
portions. One end portion 55a has righthand threads and the other
end portion 55b has lefthand threads. This forces the pivot members
54 to move in opposite directions along the rod 32 upon rotation of
the rod about its longitudinal axis to effect relative movement
between two vertebrae 22. The pivot members 54 are threaded so that
the axis of the threaded portion passes approximately through the
center of the pivot member.
The adjusting rod 32 having pivot members 54 threaded onto end
portions essentially creates a rigid link of adjustable length
which can pivot at its two end portions. The link could have just
one pivot member 54 threaded onto one end portion, while the other
end portion has a pivot member rigidly connected or integrally
formed thereon.
After the pivot members 54 are clamped by the mounting block 34, 36
and prevented from relative rotation, the adjusting rod 32 is
rotated to change the distance between two vertebrae 22. When the
rod is rotated in a first direction, because of the righthand and
lefthand threaded end portions, the distance between the pivot
members 54 will increase. If the adjusting rod 32 is rotated in a
second direction, the distance between the pivot members 54 will
decrease. The interaction of the adjusting rod 32 and pivot members
54 is similar to that of a turnbuckle. Thus, since the pivot
members 54 are connected with the vertebrae 22 by the mounting
blocks 34, 36, rotation of the adjusting rod 32 effects a change in
the relative position of the two vertebrae.
The adjusting rod 32 is rotated by gripping the hex head portion 84
(FIG. 6) with a suitable tool (not shown) and rotating the tool.
The hex head portion 84 is integrally formed on the adjusting rod
32. Alternative means for rotating the adjusting rod 32 can be
provided. For example, the adjusting rod 32 could have an
intermediate portion of the shaft itself formed with a hexagonal or
square configuration and be about the same diameter as the threaded
end portions 55a, 55b.
The mounting blocks 34, 36 (FIGS. 7 and 8) connect the pivot
members 54 with the vertebrae 22 and prevent movement of the pivot
members relative to the vertebrae. The mounting blocks 34, 36 are
designed to accept a pair of pivot members 54, as illustrated in
FIG. 7, or a single pivot member, as illustrated in FIG. 8. The
mounting blocks 34, 36 are made from a material which is compatible
with human tissue, generally a surgical grade stainless steel or
titanium.
FIG. 7 illustrates the mounting block 36 used on intermediate
vertebrae 22a, 22b (FIG. 4) for connecting a pair of spherical
pivot members 54 with the vertebrae. The mounting block 36 has a
first half 53a and a second half 62a. Each half 53a, 62a has a pair
of surfaces which define generally spherical chambers 58 for
receiving the pivot members 54. The size of the spherical chamber
58 is such that it will prevent the pivot member 54 from pivotal
movement relative to the mounting block 36 when the nut 64 is
tightened against the mounting block. That is, the diameter of the
spherical chamber 58 is equal to or slightly smaller than the
diameter of the spherical pivot member 54. This permits the
spherical chamber 58 to grip the member 54 for preventing pivotal
movement when the nut is tightened to its final position against
the mounting block.
The mounting block 36 has a first opening 88 through first side 92
and second side 94 of the mounting block 36 for receiving the force
transmitting member 52 therethrough. The first side 92 engages a
vertebra 22. The second side 94 engages the nut 64 for pressing the
mounting block 36 to the vertebra 22 and around the pivot members
54. A pair of protrusions 98 extend from the mounting block 36
around the opening 88 to add strength to the mounting block 36 and
surface area for the vertebra 22 and nut 64 to engage. The size and
configuration of the protrusions 98 depends upon the overall
dimensions of the mounting block 36 and opening 88. It will be
obvious, for example, that the protrusions 98 can have a squared or
rounded configuration.
The mounting block 36 has second and third openings 102, 104
respectively, which extend through third and fourth sides 106, 108
respectively, of the mounting block. The openings 102, 104 are
transverse to the first opening 88. The openings 102, 104 have
their longitudinal axes pass approximately through the center of
spherical chambers 58 to allow the adjusting rods 32 to pass
through for connection with the pivot members 54 and to pivot. The
openings 102, 104 are illustrated as countersunk but can be of a
cylindrical configuration. The diameter of the openings 102, 104 is
smaller than that of the spherical chamber 58 and larger than the
diameter of the adjusting rod 32. It will be obvious that it is not
necessary for the openings 102, 104 to extend completely through
the mounting block 36. For example, opening 102 could extend just
through side 106, while opening 104 could extend just through side
108.
FIG. 8 illustrates a mounting block 34 used on the extreme ends of
the assembly 20 (FIGS. 1, 4 and 5) for connecting a single
spherical pivot member 54 with a vertebra 22. The design and
function of the mounting block 34 (FIG. 8) is similar to that
described above for mounting block 36. That is, the mounting block
34 has a first half 53b and a second half 62b. A first opening 112
for receiving the force transmitting member 52 extends through both
halves 53b, 62b. The mounting block 34 has a single spherical
chamber 58a for receiving the spherical pivot member 54. A second
opening 114 extends through the top 122 and bottom 124 of the
mounting block 34 for allowing the adjusting rod 32 to pass through
and pivot relative to the mounting block. The second opening 114 is
transverse to the first opening 112.
FIG. 9 illustrates a cylindrical pivot joint 132 which allows
pivotal movement only in the dorsal plane when the mounting block
128 is connected with a vertebra 22. The mounting block 128 has a
first half 53c and a second half 62c. The mounting block 128 has a
cylindrical chamber 134 for receiving the cylindrical pivot member
132. The mounting block 128 has a first opening 136 extending
through a first side 142 and a second side 144 of the mounting
block 128.
The cylindrical configuration of the pivot member 132 prevents the
pivot member from rotating relative to the mounting block when the
adjusting rod 32 is rotated. Therefore, the force exerted by the
nut 64 on the second side 144 of the mounting block 128 is not as
critical as it would be for the spherical pivot member 54
arrangement to prevent rotation of the pivot member 54.
A second opening 152 is transverse to the first opening 136 and
extends through a third side 154 and a fourth side 156 for allowing
the adjusting rod 32 to engage the pivot member 132. The second
opening 152 is illustrated as being rectangular. It will be obvious
that the second opening 152 can also be cylindrical as described
above for mounting blocks 34 and 36 or tapered outwardly. It will
also be obvious that a mounting block can be designed that will
accept a pair of cylindrical pivot members 132 so that it can be
used as an intermediate connector in the assembly 20 illustrated in
FIG. 1.
In summary, an improved apparatus and method is provided for moving
a vertebra 22a relative to other vertebrae 22b, 22c to a desired
relationship and for maintaining the desired relationship. Mounting
blocks 34, 36 are attached to individual vertebrae 22 and
interconnected by a plurality of adjusting rods 32. Pivot members
54 are threaded onto threaded portions 55a, 55b of the adjusting
rods 32 and received in the mounting blocks 34, 36. The
relationship among vertebrae 22 is changed when the adjusting rods
32 are rotated thereby moving one vertebra relative to the other
vertebrae.
* * * * *